Geometrical inlet effects on the behavior of a non-premixed fully turbulent syngas combustion; a numerical study

This study numerically evaluates a three-dimensional, turbulent, non-premixed syngas (a mixture of H-2 and CO) flame issued from a round nozzle. The flow Reynolds number on the basis of the inlet velocity and the nozzle diameter is 16,700 and the flame is shrouded by a coflow under atmospheric conditions. A computational tool with a modified k-omega turbulence model and eddy dissipation model is used for simulating the reacting flow and its immediate surroundings. The outcomes are first compared against the existing experimental data. This reveals that when beta*, as a constant coefficient in the k-omega turbulence model, is 0.073, the numerical results match the experimental data with high accuracy. Subsequently, the effects of variations in the diameter of the inlet nozzle and its geometry are investigated. This shows that an increase in the inlet nozzle diameter leads to the downstream movement of the high-temperature region diminishing combustion efficiency. Importantly, it is shown that using the elliptical inlet nozzle with the large diameter of 1.2 based nozzle diameter (4.48 mm) assists the combustion performance and increases the maximum combustion temperature by up to 9.6%. It also results in a considerable reduction of the unburned fuels and enhances the flow residence time significantly.